Hybrid battery

8.2v NiMH smart charger in the 3 amp range... These are the same kind of smart chargers sold for RC planes, cars and drones... Also these battery packs are designed to function normally even when they're so old they only have 50% of previous capacity. So to fully restore that capacity you need to use headlight bulbs to discharge and recharge each module to deeper and deeper levels:

Stage 1 discharge: 4.8v
Stage 2 discharge: 3.0v
Stage 3 discharge: 0.6v

 

I thought those RV battery chargers also had discharge circuits?

This is the thread to learn about rebuilding your battery.

Gen II Prius Individual Battery Module Replacement | PriusChat

 

Yes, but those discharge resisters are really cheap/innacurate and soldered directly to the circuit board in most chargers and why risk heating up the board too often? Also those discharge circuits are only 10W in most cases so discharge takes a really long time compared to a 55w 12v bulb.

I start with that then switch to 20w at end of third discharge and am trying to find some 6v 35w and 20w bulbs to for the very, very end of the final discharge.

Also the lightbulb allows you to shine the light on the wall, which gives a really easy visual on current discharge status of each bulb/module...

 

As more knowledgeable PC members have correctly noted, the power (watts) INTO and OUT OF the modules should all fall within about 10% of each other compared to the average. So 100% +/- 5% = range of 10% (95% > 105% of the average), for optimal results.

This advise matches my experience spot-on, the one module that was a little off compared to the averages, but tested perfectly fine a YEAR AGO, just died. The replacement I had was also bad, but physically cracked and not internally failed.